(1) Field of the Invention
The present invention relates to a process for producing aromatic imide polymer hollow filaments. More particularly, the present invention relates to a process for producing aromatic imide polymer hollow filaments useful for separating two or more different gases, for example, hydrogen gas and carbon monoxide gas, from each other with an excellent efficiency or for concentrating the gases from a dope solution of a specific aromatic imide polymer dissolved in a specific phenolic solvent by a wet membrane-forming method.
(2) Description of the Related Art
Various methods for producing aromatic imide polymer semipermeable membranes or hollow filaments from a dope solution of an aromatic imide polymer in a phenolic solvent are disclosed by, for example, U.S. Pat. Nos. 4,378,400 for H. Makino et al and 4,378,324 for H. Makino et al.
However, the products of the methods disclosed by the above-mentioned publications are still not satisfactory in the gas-separating properties thereof. That is, the aromatic imide polymer membranes disclosed in the above-mentioned publications are used as a separating membrance for a hydrogen-carbon monoxide mixture gas. The membrance exhibits an unsatisfactory selective gas permeability (P.sub.H.sbsb.2 /P.sub.CO) of about 20 to 65 and an unsatisfactory hydrogen gas permeating rate (P.sub.H.sbsb.2) of about 1.5.times.10.sup.-5 cm.sup.3 /cm.sup.2 sec.cmHg or less.
The term "gas permeating rate" used herein is defined as follows. EQU Gas permeating rate (cm.sup.3 /cm.sup.2.sec.cmHg).times.X/(A.times.T.times.D)
wherein X represents an amount (volume) in cm.sup.3 of the gas passed through a membrane. A represents a surface area in cm.sup.2 of the membrane through which the gas passed T represents a transmission time in sec. of the gas through the membrane and D represents a difference in pressure in cmHg between the gas-supply side and the opposite side of the membrane.
Accordingly, it is strongly desirable to provide a process for producing aromatic imide polymer hollow filaments which are useful as gas-separating hollow filaments having an excellent gas selective permeability and a superior hydrogen gas permeating rate (P.sub.H.sbsb.2).